Composite building structure and walls therefor

ABSTRACT

A composite flexible-rigid building structure comprising a flexible skeleton structure and a plurality of bearing wall members having slits formed therein. The overall composite building structure normally behaves as a rigid structure for load smaller than a certain predetermined magntidue but transfers to a flexible structure upon occurrence of an extremely heavy load in excess of said magnitude. Each slit wall member normally acts as a rigid frame structure, and has a large ductility so as to absorb a large amount of seismic energy after being yielded at a certain predetermined load before complete failure.

Uited States Patent [191 [111 3,736,712 Muto et al. [451 June 5, 1973[54] COMPOSITE BUILDING STRUCTURE OTHER PUBLICATIONS AND WALLS THEREFORJournal of American Concrete Institute, pages [75] Inventors: KiyoshiMuto; Takao Itoh; Nobutsu- 909-918 June 1962.

all of Tokyo, Japan Engineering News-Record Jan. 9, 1947 pages 83, 84.[73] Assignee: Kajima Corporation, Tokyo, Japan i PrimaryExaminer-Alfred C. Perham [22] plied" 1972 Attorney-Roberts B. Larson,Andrew E. Taylor, [21] Appl. No.: 229,964 William R. Hinds et al.

Related US. Application Data [57] ABSTRACT I Continuation-impart of 5811March 6, A composite flexible-rigid building structure compris- 1970*abandoned ing a flexible skeleton structure and a plurality of bearingwall members having slits formed therein. The ..52/l6E7645h25/ overallcomposite building Structure normally behaves [58] Field of Search..52/l67,573, 198 as a Smaller than a i predetermined magntidue buttransfers to a flexible [56] References Cited structure upon occurrenceof an extremely heavy load in excess of said magnitude. Each slit wallmember T D A E PATENTS normally acts as a rigid frame structure, and hasa 845,046 2/1907 Bechtold ..52/l67 larlgfductmy as to a large amount 91,474,827 11/1923 Jones .52/174x seismic energy after being yielded at acertain 2,166,577 7/1939 Beckius ..52/l67 X predetermined l ad bef recomple e failure. 2,950,576 8/1960 Rubenstein ..52/l67X 16 Claims, 31Drawing Figures D D D D D I I I I r Li I I I J I I I I I I I I I I I I Bl I I I I I I I l I N I I I II I PAIENIEUJUH 5l975 $736,712

FIGJ lb PAIENIEUJUH 5191s SHEEI 5 [IF 9 PATENTEUJUH 5197s SHEET 7 BF 9Mmmm-8642O Period, T (seconds) FIG.I3

Deformation (strain) FIG.I5

COMPOSITE BUILDING STRUCTURE AND WALLS THEREFOR This application is acontinuation in part of application Ser. No. 17,062 filed March 6, 1970and now abandoned.

This invention relates to a composite rigid-flexible building structureand a composite wall structure therefor. More particularly, the presentinvention relates to a composite rigid-flexible building structureapplicable to a very tall multistoried building and a special wallstructure therefor, which structure incorporates a plurality rows ofslender slit walls vertically extending throughout the entire height ofthe building with suitable intervals between each other, whereby therigidity of the structure varies in response to application of verylarge load thereto, e.g., an extremely large seismic force.

Generally speaking, the aseismatic structure of a very tall building isrequired to meet the following conditions.

1. The structure will not experience any excessively large deformationin the case of normally expected winds and frequently occurringearthquakes.

2. The structure should be capable of tenaciously bear sizeabledeformations, if such deformations should be caused by rarely-happeningextra heavy earthquakes.

3. The structure should warrant the necessary and sufficient levels ofbearing strength.

4. The damping effects of a building skeleton, consisting of steelmembers alone, can be improved by using steel-reinforced concrete walls.The oscillation-absorbing effects and the specific bearing strength ofsuch structure can further be improved as cracks are dispersedextensively throughout the concrete wall.

The inventors have succeeded in developing a composite rigid-flexiblestructure satisfying the aforesaid requirements. According to thepresent invention, there is provided a composite rigid-flexiblestructure for a multi-storied building, which comprises a steel skeletonand special steel reinforced concrete wall structures with slits, thewall structures being substantially integrally secured to the skeletonat each story. What is meant by the wall structure with slits" refers toa steel reinforced concrete wall structure which includes subsectionsseparated by a plurality of pairs of mutually slidable abutting surfaceswhich are disposed in the wall structure in parallel with each other.Each pair of the mutually slidable surfaces is formed by embedding oneor more strap-like members in the wall structure. The pair of mutuallyslidable surfaces defines a kind of slit, but the two surfaces abut witheach other in such a manner that the abutting two surfaces do not allowair passage between them under normal conditions. The wall structuresbeing cast in site or precast at works by using concrete having a highbearing strength against shearing while forming suitable slits therein.In one embodiment of the invention the wall structures thus formed aresecured to the steel skeleton in a number of vertically extending groupsat suitable intervals, each group consisting of two'or more rows of thewall structures extending vertically from the top to the bottom of theskeleton between a pair of adjacent columns of the skeleton. The steelskeleton is made by using shaped steels, such as H-shaped steels,boxshaped steels, cross steels, and the like.

Generally speaking, conventional aseismatic building structures userigid wall members in order to prevent deformation of skeleton by therigidity of the wall members, and to improve the strength of theskeleton. On the other hand, if the rigidity of the walls of a very tallmultistoried building is too high, seismic load to the building becomestoo large to adopt wall design with an economical cross section. Thus,the use of wall members with a large cross section tends to impair theelastic deformation characteristics of the structure.

In short, for extra-heavy earthquakes, which occur only very rarely, theso-called flexible structure without any highly rigid wall members ispreferable. The flexible structure has a comparatively long period ofits natural vibration and allows a comparatively large interstorydeformation, or deformation between adjacent stories of the building.Accordingly, the flexible structure can deal with huge energy of veryrare extra-heavy earthquakes, without using any massive skeleton.

On the other hand, for comparatively frequently occurring less heavyearthquakes and for strong winds, a rigid structure is more practicaland preferable to the flexible structure, because the former allows onlya small amplitude of vibration for such less heavy earthquakes andwinds, as compared with that of the latter.

Therefore, an object of the present invention is to provide an idealcomposite structure for very tall multistoried buildings, which normallyacts as a rigid structure, but upon occurrence of an extra-heavyearthquakes, transfers to a flexible structure, so as to ensure adesired high bearing strength while allowing desirable deformations.Such transfer from the rigid construction to the flexible constructioncan be effected by releasing the rigidity of the wall members of therigid structure upon occurrence of the aforesaid extraheavy earthquake.

In a steel reinforced concrete wall structure, precast or cast-in-site,if the dynamic strength of the wall structure is not continuous butsuitably distributed with intermittent strong and weak portions, thewall structure may normally behave as a rigid structure but maycompletely lose its shearing strength upon application of a shearingload surpassing a certain level. More particularly, such wall structuremay act as a rigid-frame, from the dynamic standpoint, for shearingloads of frequently occurring magnitude. Upon occurrence of anextra-heavy earthquake with an extremely large acceleration, however,the weak portions of the wall structure may yield, so that the overallstrength of the wall structure may gradually varies, until the shearingstrength of the wall structure is completely lost. If such wallstructures are incorporated in building with a steel skeleton offlexible structure, and if the wall structures are so designed as tonormally behave as rigid-frames but to completely lose their rigidity ata predetermined shearing load, the overall building structure willbecome rigid for normal load with a frequently occurring magnitude,while upon occurrence of extremely heavy load surpassing a certainpredetermined magnitude, the building structure will become flexible.

The wall structure with the aforesaid distributed strength can beconstructed by disposing weakened portions in the wall structure atcertain intervals.

Therefore, another object of the present invention is to provide a wallstructure which normally behaves as a rigid structure, but completelyyields upon application of an extremely heavy shearing load in excess ofa certain predetermined level.

For a better understanding of the invention, reference is made to theaccompanying drawings, in which:

FIGS. Ia and lb are diagrammatic illustrations of the manner in which aconventional rigid wall yields upon application of a heavy shearingload;

FIGS. 2a and 2b are views similar to FIGS. la and 1b, illustrating themanner in which a wall with slits is deformed by application of a heavyshearing load;

FIG. 3 is a graph, illustrating the relation between load P anddeformation '0, in the walls of FIGS. Ia, lb, and FIGS. 2a, 2b;

FIGS. 4a to 4d are schematic elevations, illustrating differentdispositions of slits in a steel reinforced concrete wall structure,according to the present invention;

FIG. 5 is a schematic plan view of a known building structure,illustrating the disposition of walls therein;

FIGS. 6 to 8 are schematic plan views of different embodiments of thepresent invention, illustrating the disposition of walls of specialstructure, respectively;

FIG. 9 is a schematic elevation of an embodiment of the presentinvention, illustrating a disposition of special wall structures in acomposite building structure;

FIG. 10 is a schematic elevation of a wall structure, according to thepresent invention;

FIGS. 111a and 11b are detailed partial sectional views of the wallstructure of FIG. 10;

FIG. 110 is a side view of the wall structure of FIG. I0;

FIG. 12 is a graph, illustrating the relation between the height of abuilding and its natural period of vibration;

FIG. 13 is a schematic diagram, showing a typical range ofdiscomfortable building swaying;

FIG. I4 is a graph showing typical values of earthquake acceleration atdifferent periods, or vibratory frequencies, of earthquake vibration;

FIG. 15 is a graph showing the stress-strain characteristics of a knownrigid building structure and a composite building structure, accordingto the present invention;

FIGS. Ma and 16b are graphs, showing ductility characteristics of slitwall structure, for different slit dispositions; and

FIGS. 17a to 17g are fragmentary sectional views, illustrating differentconstructions of a slit, to be incorporated in the wall structureaccording to the present invention, respectively.

Before entering the details of slit wall members to be used in thestructure of the present invention, the basic principles of seismiccomposite building structures will be described.

Generally speaking, a steel building skeleton has its natural(fundamental) period of vibration, as shown in FIG. 12. The approximatenatural period T seconds of a skeleton of height H meters is given bythe following relation.

T=aH

here, a is a constant related to the rigidity of the skeleton.

What the equation (1) means is simply that, for a given height of theskeleton, its natural period is proportional to its rigidity. Theinventors found that for most tall buildings, the aforesaid constant ais greater than 0.025 for suppressing the earthquake load to theskeleton as will be described hereinafter.

When a tall building is exposed to strong earthquakes, it sways, anddwellers of the building may feel discomfort as the magnitude of theswaying increases. It is reported that the discomfort depends both onthe period of the swaying and on the magnitude of the acceleration anddisplacement of the swaying. FIG. I3 reproduces one of such report,i.e., Wind and Movement in Tall Buildings by FU-KUEI CHANG, Journal ofCivil Engineering-ASCE, Aug. 1967. For instance, referring to FIG. 13,when a swaying is caused at a period of 4 seconds, or at a rate of 0.25cycle per second, the dwellers do not usually feel any discomfort aslong as the magnitude of swaying, or displacement 8, is less than about2 inches. However, the dwellers feel annoying discomfort for swayings ofgreater than 2 inches at 0.25 cycle per second, if the acceleration iskept constant at 1.5 percent g (g being gravitational acceleration).

' As a design basis for removing such discomfort, the inventorstranslated the annoying range of FIG. 13 to a tolerable discomfortrange, as shown by the dotted lines of FIG. 12. The procedure of thetranslation is as follows.

i. In FIG. 13, an average annoying limit was determined as shown by thedash-dot lines. With such average annoying limit of FIG. 13 in mind, forthe period of 3 seconds, the maximum allowable displacement 8 is 2inches (about 5 cm), and for 4 seconds of period, the maximum allowabledisplacement is about 4 inches (about 10 cm).

ii. It is known that the aforesaid displacement 8 is proportional to thebuilding height H and the initial rigidity of the skeleton, as given bythe-following equation.

here, R is a constant related to the initial rigidity of the skeleton.

The typical value of R is about 0.001 for usual tall buildings.

Thus, the maximum allowable height of the skeleton for a given maximumallowable displacement 6 is given by H=8/R. For instance, for 8 of 5 cm,H is 50 meters, and for 8 of 10cm, H is meters.

Since such maximum allowable displacements correspond to the naturalperiods of the skeleton, the average annoying limit curve of FIG. 13 canbe translated into the plane of FIG. 12, point by point, e.g., for T=3seconds, H=50 meters, and for T=4 seconds, T=l 00 meters. Thus, theinventors have found that the tolerable discomfort limit may, forinstance, be given by It should be noted here that such limit depends onmany factors, such as the rigidity of the skeleton,

- the annoying range of dwellers, etc.

Accordingly, the equation (3) is just an indication,

but does not have any limiting significance.

Referring to FIG. 14, earthquakes have different periods and differentshearing forces. Based on statistics, the heavy solid curve of FIG. 14is recommended by professional organizations as the basis for aseismaticstructural design. What the curve of FIG. 14 means is that earthquakeswith a short period have a large shearing force. As compared with a unitshear force for about 2.5 second period, the shear force of earthquakeof 1 second period is 4 units, or four times as great.

Accordingly, building skeletons should not have a short natural period,because a skeleton with a short natural period tends to resonate withearthquake vibration of short period, and is exposed to a large shearforce. Thus, for a tall building, the skeleton has to be flexible, andshould not be rigid. This is why the constant a of the equation (1) isusually selected to be greater than 0.025 for tall buildings.

Referring to FIG. 12, if a skeleton having a constant a of greater than0.025 becomes very tall, or the height H becomes large, the displacement8 of the skeleton due to winds and minor earthquakes falls in theaforesaid discomfort range. In order to mitigate this difficulty, it hasbeen a practice to increase the rigidity of the building structure forreducing its natural period T by reducing the a value. However, theincreased rigidity inevitably reduces the natural period of thestructure, inviting an increased earthquake load as a result. To providefor the high earthquake load, the building structure was made very heavyand expensive in past design.

As an example, a flexible skeleton having a natural periodcharacteristics of T=0.035H will be considered. When this skeleton isused for a building of 170 meter height, its wind or earthquakedisplacement exceeds tolerable discomfort limit, as shown by the pointP1 of FIG. 12. According to the conventional practice, the rigidity ofthe skeleton is increased by adding brace members or monolithic walls,for instance to the point P2 of FIG. 12. The structure of the point P2has a natural period T of about 1.7 second, to which period theearthquake shear force of about 1.75 unit is recommended as a designbase. The monolithic reinforcedwalls cannot bear such shear force, aswill be explained hereinafter. Thus, expensive structural materials,such as steel braces, must be used to achieve the desired increase ofthe rigidity, to make the building costly.

What the present invention intends to accomplish is to add the slitwalls to the skeleton of the point P1, so as to shift it to the pointP3, as shown in FIG. 12. For the structure of the point P3, the naturalperiod is about 2.5 seconds, and the recommended shear force is about0.80 unit, as shown in FIG. 14.

It is apparent from FIG. that the structure of the point P3 withstandsuch shear force. If the structure of the point P3 is exposed to theearthquake causing the shear force of 1.75 unit, it will be deformed tothe point B2 of FIG. 15, but it bears the shearing load. As a result,the H-T characteristics of the structure of the point P3 may be shiftedto point P4 of FIG. 12.

Theoretically, it is possible to increase the rigidity of the structureof the point P1 of FIG. 12 to the point P3 by using ventilation walls,such as those disclosed by HE. Jones in his U.S. Pat. No. 1,474,827.However, with such ventilation walls, the structure cannot withstand theshear load of, e.g., 1.75 unit, as described hereinafter by referring toFIG. 15. In this case, the structure of the point P3 of FIG. 12 isdirectly shifted back to the original point P1, but cannot stop at anyintermediate point between P3 and P1. In fact, the structure withventilation walls collapses when the shear force exceeds 1.0 unit.

Referring to FIG. 15, the curves A, B, and C represent stress-straincharacteristics of a flexible skeleton, a first composite structurehaving the flexible skeleton plus the slit walls, a second compositestructure having the flexible skeleton and the monolithicreinforcedwalls, respectively. When an earthquake shear force of about1.75 unit, in terms of normalized shear force based on the shear forcefor earthquake vibration of about 2.5 second period (FIG. 14), isapplied to the second composite structure represented by the curve C ofFIG. 15, the monolithic reinforced wall cannot withstand the shear forceand completely collapses (due to brittle failure), so that the remainingflexible skeleton of the second composite structure, as represented bythe curve A of steel skeleton alone, tries to bear this shear force butthe skeleton collapses at the point X.

.Thus, the entire second composite structure collapses.

This means the monolithic reinforced-walls cannot withstand suchearthquakes.

On the other hand, when the same earthquake shear force of about 1.75unit is applied to the first composite structure as represented by thecurve B of FIG. 15, the slit walls yield at the point B1, but thecomposite structure tries to bear the shear force with the strength ofthe flexible skeleton plus the ductility of the slit wall. Consequently,this first composite structure bears the shearing force of about 1.75unit at the point B2 of FIG. 15. The first structure can bear shearforces up to the point Y of FIG. 15. In short, the slit walls are freefrom the so-called brittle failure, but they are ductile.

Such anti-earthquake strength cannot be achieved by the ventilationwalls, because ventilation wall completely collapses at the point B1 ofFIG. 15, and the entire load is shifted to the flexible skeleton A.

After such large shear force is removed; or after the heaviestearthquake load is over, the cracked slit walls may be replaced. It isapparent that the reconstruction of the completely collapsed secondcomposite structure is much more costly than the replacement of the slitwalls. Above all, the first structure with the slit walls is much saferfor dwellers than the second structure, because the former withstandlarger earthquake shear forces than the latter.

The slit wall to be used for providing the desired composite flexiblestrain-stress characteristics, as shown by the curve B of FIG. 15, willnow bedescribed.

FIG. 1a shows a solid wall structure A without slits, while FIG. 2ashowsa composite wall structure B with a plurality of slits S formedtherein. If a shearing load Pa is applied to the solid wall structure A,as shown in FIG. la, there is produced a deformation 8,, as shown inFIG. lb. In the case of the solid wall structure A without any slits,large cracks C are suddenly generated before the deformation 8,,increases to a material magnitude. FIG. 3, Curve A illustrates suchrelation between the load P and the deformation 8 of the wall structureA.

Upon application of shearing load Pb to the composite wall structure Bwith slits S, as shown in FIG. 2a, there isproduced a deformation 8,, asshown in FIG. 2b.

With the slit wall B according to the present invention, the criticaldeformation 8,, at which the wall structure begins to crack, is muchlarger than the corresponding critical deformation 8,, for the knownsolid wall A, as shown in FIG. 3. The loads corresponding to thecritical deformation 8 8,, or yielding strengths of the walls A, B, areshown by Pa, Pb, respectively.

After the beginning of the cracking, the cracks in the wall structuregrowfas the load thereto increases, until the cracks spread throughoutthe wall structure. If the load to the wall further increases, the wallstructure soon fails in the case of the conventional wall A. With theslit wall B, according to the present invention, the wall structurefurther deforms even after its yield or after the cracks are spreadtherethrough. The ability of the wall to deform after its cracking isusually referred to as ductility. In FIG. 3, the critical load at theboundary between the cracking deformation and the ductility deformationis represented by Pa for the conventional wall A, and by Pb" for theslit wall B according to the present invention.

It is apparent from FIG. 3 that the conventional wall A fails soon afterthe end of its cracking, because it has little ductility. On the otherhand, the slit wall B according to the present invention has a largeductility, so that it experiences a considerably large deformation afterthe end of its cracking deformation before its failure or rupture,absorbing more earthquake energy, even though the maximum strength ofthe slit wall is smaller than ordinary monolithic walls. Thus thecritical safety is assured by this invention.

One of the important features of the slit wall B, according to thepresent invention, is in that it can absorb a noticeable amount ofenergy during the period from the moment when it begins to be cracked toits complete failure or rupture. The rupture strength of the slit wallB, or the load at which the wall B is failed, is represented by a symbolD while the corresponding rupture strength of the conventional solidwall A is shown by a symbol D in FIG. 3.

If the rupture strength D, as defined in FIG. 3, is so selected as torepresent the individual wall structures share of that specific load toa building structure, which necessitates the transfer of the dynamicalnature of the building structure from rigid to flexible, it is possibleto provide an ideal building structure that normally behaves as a rigidstructure for comparatively small loads, but transfers to a flexiblestructure upon occurrence of an extremely heavy load in excess of theaforesaid specific load. The magnitude of the rupture strength D ofindividual composite wall structure can be controlled by suitablyadjusting the number and the shape of the slits S.

The composite wall structure B with slits S, as shown in FIG. 20, can bemade of a precast concrete wall or a cast-in-site concrete wall. I

The composite wall structure will now be described in further detail,referring to FIGS. 10 to 1 1c and FIGS. 17a to 17 In FIGS. 10, Ha, 11b,and 110, a building skeleton consists of columns 1 and beams 2, and wallstructures are fitted in lattice spaces defined by the columns andbeams. For simplicitys sake, two different kinds of wall structures,both embodying the present invention, are shown in one elevation of FIG.10. The left-hand portion of FIG. 10 partially illustrates a castin-sitewall structure 3 with steel reinforcement, while the right-hand portionof the figure shows a wall structure including two or more precastconcrete wall sections 4, also with steel reinforcement. Steel bars 5are used for the reinforcement, as is shown in FIG. Ill.

In both cases of precast and cast-in-site concrete wall structure 3, aplurality of slits 6 are formed in the wall structure, in parallel witheach other at suitable intervals. Preferably, a part of the wallstructure 3 is left continuous in one direction across the entire span,despite the presence of the slit 6; for instance, the upper and bottomedges, as shown in FIG. 10.

In the case of the wall structure including the precast wall sections 4,mutually abutting edges of the adjacent wall sections 4 are bondedtogether at suitable spaced positions, as portions 7 of FIG. 10, whileforming slits 6 therebetween. The connection of the precast wallsections 4 to the building skeleton, directly or indirectly, is effectedby applying cement mortar grout 7 between the top and bottom edges ofthe wall sections 4 and the building skeleton members. The bondingportions 7 between the adjacent precast wall sections 4 are made, forinstance, by providing projecting steel rods 5 at such portions of eachwall section 4 and welding the projecting rods 5 at the portions 7 Aspointed out in the foregoing, each slit 6 in the wall structureaccording to the present invention is made by forming mutually slidableabutting surfaces at the position of the slit 6. FIGS. 17a to 17gare-sectional views of different wall structure B, illustrating themanner in which such sliding surfaces are formed. Referring to FIG. 17a,a pair of strap-like bar members Sm are embedded in each slit portion 6of the wall structure B, in such a manner that the bar members Sm areintegrally secured to the wall structure B, but the two bar members Smare slidable with each other while forming mutually slidable surfaces atthe abutting portions thereof. Such mutually slidable surfaces form aslit 6, as shown in FIG. 17a. The two mutually slidable surfaces at eachslit 6 abut with each other in such a fashion that no air passage isnormally expected through the gap therebetween.

-It is an important feature of the present invention that the wallstructure B is divided into a plurality of subsections by such slits 6.As a result, if the rigidity of the wall structure B is measured atdifferent points thereof, the rigidity at a point in the subsection willbe different from that at the slit 6. Thus, the slit wall structure Bhas a discontinuous distribution of rigidity. Nevertheless, the slitwall structure B behaves as an integral member for a load within acertain limit; namely, for any loads smaller than the yielding stress ofthe wall structure B. When a load in excess of its yielding stress isapplied to the wall structure B, the individual subsections, each beingdefined by the adjacent slits 6, tend to behave somewhat separately. Allthe subsections are, however, bonded together at a certain portionthereof, as pointed out in the foregoing. As a result, the individualsubsections tend to swell in response to the load in excess of theyielding stress. The mutually slidable abutting surfaces at each slit 6,however, act to resist against such swelling. Consequently, the slitwall structure B according to the present invention has a highductility; namely, the slit wall structure undergoes a considerablylarge deformation after being yielded but before being broken down.Referring to FIG. 3, the magnitude of such ductility is defined asfollows.

ductility rupturing deformation 8 lyielding deformation 8,,

In order to achieve a large ductility, as defined above, it ispreferable to dispose the reinforcing steel rods in the subsection insuch a manner that shearing breakdown stress (Kg/cm of the subsection isgreater than bending yielding stress (Kg/cm) thereof.

The magnitude of the above defined ductility depends on the size and thedisposition of the slits 6 in the wall structure B. Referring to FIG.4a, slits 6 of length I may be disposed in the wall structure B inparallel with one edge of the wall structure, while leaving spacings lfrom the longitudinal ends of the slits 6 to facing edges of the wallstructure B. The slits 6 may be spaced by uniform distances D betweenadjacent slits and between the edge of the wall structure B and thenearest slit 6. Tests were made on the effects of different slitdispositions, by measuring the following sway deformation angle R(radian) for sample slit walls having different dimensions.

here,

8, is rupturing deformation of the slit, and l is the length of theslit.

The results are shown in the following Table and FIGS. 16a and 16b.

TABLE R i' 15 D L 1 Ductility (5111. 5111. 515. l/D 15 1) 10 40. s 51151. 0 1.15 0. 559 14. 55 5. 40.8 01. 151. 0 1.15 0.000 14. 05 5. 40. s51 151. 5 1.15 o. 059 15. 84 0. 49. 5 55 245 0. 00 0. 750 8.9 a. 36 24132 2. 5 I. 500 25. 56 6. 36 24 132 2. 5 1. 500 20. 99 3. 35 27 132 2.22 1. 333 22. 59 5. 36 30 132 2. 0 1. 200 16. 5 2. a5 30 132 2. 0 1. 20019. 75 a. as as 132 1.82 1.001 17.18 1. 36 33 132 1. 82 1. 091 20. 42 4.39.0 2.15 152.0 2.512 1.514 25. 052 a. 39. 0 21. 6 132. 0 2. 512 1. 81428. 693 4. 30.0 27.0 132.0 2.000 1.444 22.049 3. a9. 0 27. 0 132. 0 2.000 1. 444 22. 400 4. 3a. 0 20. 5 132. 0 2. 491 1. 245 10. 700 s. 33. 020. 5 1:12. 0 2. 401 1. 245 17. 300 4. 33. 0 33. 0 132. 0 2. 000 1.00018.202 3. 33. 0 33. 0 132. 0 2.000 1.000 20.000 4.

The inventors have found out that, for purposes of aseismaticstructures, the aforesaid sway deformation angle R should preferably begreater than 14X10". To obtain such rupturing angular deformation, thefollowing conditions must be satisfied, provided that the slitdisposition as shown in FIG. 4a is used.

l /D 0.5 and l/D 1.0

The strapJike bar members S, for making the slit 6, as shown in FIG.17a, is made of hard yet flexible material, which can form a slidablesurface. Typical examples of such material include asbestos slates,plaster boards, synthetic resin, iron, and non-ferrous metals.

The construction of the individual slit 6 is not restricted to that asshown in FIG. 17a. Although the embodiment of FIG. includes the slit 6extending through the entire thickness of the wall structure B, it isalso possible to leave non-slitted portion or portions S, in itsthickness, as shown in FIGS. 17b and 171:. Suitable sealing material S,may be applied to opposite edges of the mutually slidable abuttingsurfaces at the slit 6, as shown in FIGS. 17d and 17e. The slit 6 ofFIG. 17d is almost as thick as the wall structure 8 itself, while thethickness of the slit 6 of the FIG. l7e represents only a small fractionof the thickness of the wall structure. FIG. 17f shows a slit 6 made byusing only one metallic strap 8,, coated with frictionreducing films Sthereon. FIG. 17g illustrates a slit construction, in which a metallicstrap 8,, is sandwiched by a pair of non-metallic strap-like bar membersS at the junction between two adjacent subsections of the wall structureB.

FIG. 4b shows a modification of the slit disposition of FIG. 4a bydividing each slit 6 into two parts which are spaced from each other inthe longitudinal direction thereof. In the embodiment of FIG. 40, theslits 6 extend from one edge of the wall structure and terminate atabout the central portion of the wall structure B, while FIG. 4dillustrates another slit disposition in which slits extend from oppositeedges of the wall structure B and terminate at an intermediate portionof the wall structure B, so as to leave a suitable spacing between theextended ends of the slits 6. In other words, the length of each slit 6is shorter than the distance between the opposite edges of the wallbody, in the case of FIG. 4c; and the length of the slit 6 is shorterthan one half of the distance between the opposite edges.

Thus, by incorporating those slit wall structures in a flexible skeletonstructure, it is possible to provide a composite building structure,which behaves as a rigid structure by the initial rigidity of the wallstructures for rather frequently occurring heavy seismic or wind load,but transfers to a flexible structure by yielding the wall structuresupon occurrence of an extremely heavy rare seismic load. With the wallstructures B of FIG. 2a, the entire wall of the composite buildingstructure yields at a certain load and smoothly transfers to breakdown.Thus, the overall building structure smoothly and continuously transfersto the desired flexible structure. The wall structure B also ensuresformation of a reliable flexible structure after being yielded.

FIG. 5 shows a schematic plan view of a building skeleton, according toa known system, which incorporates wall structures A without any slits.With conventional wall structures as depicted in FIG. 5, the desiredaseismatic strength cannot be achieved. If slit wall structures A aredisposed in a manner similar to FIG. 5, the building strength willsomewhat be improved.

FIGS. 6 to 8 are schematic plan views of different embodiments of thecomposite building structure of the present invention, respectively. Inthe composite building structure of the invention, selected spans, eachdefined by adjacent steel columns, are vertically subdivided, so that aplurality rows of the slit wall structures B (two rows in theillustrated embodiments) are vertically disposed in each of the selectedspans. Each row of the slit wall structures B extends verticallythroughout the full height of the building, as shown in FIG. 9.

structure.

Conventional rigid building structure.

(FIG.

incapable of following large deformation.

Earthquake energy absorption is comparatively low, and hence,comparatively less safe.

Excessively large deformation is forcibly caused by the boundary beameffects.

Due to the concentration of rigid wall sections, stress level is high.

Due to the load concentration at rigid walls, stress distribution in theskeleton Composite building structure of the invention.

(FIGS. 6 to 10) Capable of following both small and large deformations.Earthquake energy absorption is comparatively high, and hence,comparatively safer.

The boundary beam effects are of reasonable magnitude.

Due to the distributed combination of wall structures with slits andskeleton, stress level is low.

Due to the load sharing to the skeleton, stress distribution between theskeleton and walls becomes and walls is uneven.

. even.

In other words, conventional rigid building structure with non-slenderbearing walls, as shown in FIG. 5, is susceptible to bendingdeformation. Accordingly, excessively large stress is caused at lowerstories, while excessively high reaction to bending of the skelton isgenerated at upper stories. Consequently, the conventional rigidbuilding structure is less reliable and requires more steel structuralmaterial, resulting in an increased cost. Besides, floors at higherstories of the conventional building structure tend to considerablyincline and horizontally move, in response to heavy loads. As a result,the habitability, or comfortableness, at the higher stories of theconventional building structure is inferior. The conventional buildingstructure is also prone to breakdown due to excessive energyconcentration therein.

On the other hand, the composite building structure of the presentinvention including wall structures with slits disposed in spacedvertical rows, as shown in FIGS. 6, 7, 8, 9, and 11, produces shearingdeformation upon application of load thereto. The inclination andhorizontal displacement at higher stories of the composite buildingstructure of the invention are small. The stress caused in the compositebuilding structure is comparatively small, to provide an improvedbearing strength. In short, the composite building structure of thepresent invention fully utilizes the advantages of the flexiblestructure, while retaining the rigidity necessary for frequentlyoccurring low stresses. Furthermore, with the composite structure of thepresent invention, the period of the natural vibration can easily becontrolled, while maximizing the energy absorption therein.

Thus, the invention contribues greatly to the industry.

What is claimed is: I

I. A steel reinforced concrete wall having a discontinuous distributionof rigidity, comprising a concrete wall body;

steel reinforcing members distributed in the concrete wall body toreinforce the body;

a plurality of elongated strap-like bar members, each.

having at least one elongated surface whose width taken in the directionof the thickness of the concrete wall body being substantially identicalwith the thickness of the concrete wall body, said plurality of the barmembers being embedded in said concrete wall body in parallel with eachother; a plurality of pairs of mutually slidable abutting surfacesdistributed in said concrete wall member in parallel with each other, atleast one of each pair of abutting surfaces being formed by theelongated surface of said bar member; and plurality of subsections ofthe concrete wall member being defined by severing said concrete wallbody and said reinforcing members at said pairs of mutually slidableabutting surfaces, in such a manner that the concrete wall member has arigidity which is discontinuous at said abutting surfaces and yet theconcrete wall member being a rigid integral wall as a whole unless ashearing load in excess of a certain yielding stress is applied thereto;the longitudinal length of said abutting surfaces and the distributionof said steel reinforcing members being so related that said abuttingsurfaces act to prevent each subsection from swelling when a stressgreater than said yielding stress but smaller than a breakdown stressthereof is applied thereto. 2. A steel reinforced concrete wallaccording to claim 1, wherein said reinforcing concrete members in eachsubsection being so distributed that each subsection has a shearingbreakdown stress (Kg/cm) which is greater than a bending yielding stress(Kglcm of the same subsection. v

3. A steel reinforced concrete wall according to claim 2, wherein eachof said subsection has a ductility factor not smaller than three, saidductility factor being a (strain at breakdown)/(strain at yield) ratio.

4. A composite building structure having a skeleton with a breakdownstrain 0-,(radians) and a plurality of steel reinforced concrete wallsjoined to said skeleton, each of said steel reinforced concrete walls,comprising a concrete wall body;

steel reinforcing members distributed in the concrete wall body toreinforce the body;

a plurality of elongated strap-like bar members, each having at leastone elongated surface whose width taken in the direction of thethickness of the concrete wall body being substantially identical withthe thickness of the concrete wall body, said plurality of the barmembers being embedded in said concrete wall body in parallel with eachother;

a plurality of pairs of mutually slidable abutting surfaces distributedin said concrete wall member in parallel with each other, at least oneof each pair of abutting surfaces being formed by the elongated surfaceof said bar member; and

a plurality of subsections of the concrete wall member being defined bysevering said concrete wall body and said reinforcing members at saidpairs of mutually slidable abutting surfaces, in such a manner that theconcrete wall member has a rigidity which is discontinuous at saidabutting surfaces and yet the concrete wall member being a rigidintegral wall as a whole unless a shearing load in excess of a certainyielding stress is applied thereto;

the longitudinal length of said abutting surfaces and the distributionof said steel reinforcing members being so related that said abuttingsurfaces act to prevent each subsection from swelling when a stressgreater than said yielding stress but smaller than a breakdown stressthereof is applied thereto, said reinforcing concrete members in eachsubsection being so distributed that each subsection has a shearingbreakdown stress (Kg/cm which is greater than a bending yielding stress(Kg/cm of the same subsection, and

a ductility factor not smaller than three, said ductility factor being a(strain a (radian) at breakdown)/(- strain o' (radian) at yield) ratio,whereby said composite building structure has a breakdown strain a(radian) which is identical with the sum of said skeleton breakdownstrain o-,(radian) and said wall subsection breakdown strain raidan)(o';,=o' +0' 5. A steel reinforced concrete wall according to claim 1,wherein each of said bar members is made of a material selected from thegroup consisting of asbestos slates, plaster boards, synthetic resin,iron, and nonferrous metals.

6. A steel reinforced concrete wall according to claim 5, wherein eachof said bar members consists of a single bar made of a material selectedfrom said group.

7. A steel reinforced concrete wall according to claim 5, wherein eachof said bar members consists of two bars made of a material selectedfrom said group.

8. A steel reinforced concrete wall according to claim 1, wherein saidconcrete wall body is of rectangular shape including one side length of(1+ 2l ),and the length of each of said strap-like bar members is l, andthe bar members are disposed in said concrete wall member with a uniformspacings of D between each other in parallel with said wall member sideof length (l l while leaving a spacing 1 from other sides of the wallmember to facing ends of the bar member, the dimensions D, l, and lsatisfying conditions of l /D 0.5 and l/D l.0..

9. A composite wall structure according to claim 4, wherein naturalperiod T (second) of the skeleton is related to the height H (meter) ofthe skeleton as follows: T 0.025H.

10. A composite building structure according to claim 4, wherein saidskeleton is a steel skeleton.

11. A steel reinforced concrete wall according to claim 1, wherein saidsubsections are precast steel rein- I forced concrete wall sections, andsaid strap-like bar members are disposed at joints between the adjacentprecast wall sections.

12. A composite wall structure according to claim 4, wherein said steelreinforced concrete wall members are disposed in at least two verticalrows in parallel with vertical columns of said skeleton.

. 13. A steel reinforced concrete wall according to claim 1, whereinsaid strap-like bar member is coated with a friction-reducing film.

14. A steel reinforced concrete wall according to claim 8, wherein eachsaid strap-like bar members is divided in two parts which are spacedfrom each other in the longitudinal direction thereof.

15. A steel reinforced concrete wall according to claim 1, wherein saidstrap-like bar members extend from one edge of the wall body toward theopposite edge to said one edge and terminate at an intermediate positionbefore reaching the opposite edge.

16. A steel reinforced concrete wall according to claim 1, wherein saidstrap-like bar members extend from each of the two opposing edges of thewall body by a length shorter than one half of the distance between thetwo opposing edges.

1. A steel reinforced concrete wall having a discontinuous distributionof rigidity, comprising a concrete wall body; steel reinforcing membersdistributed in the concrete wall body to reinforce the body; a pluralityof elongated strap-like bar members, each having at least one elongatedsurface whose width taken in the direction of the thickness of theconcrete wall body being substantially identical with the thickness ofthe concrete wall body, said plurality of the bar members being embeddedin said concrete wall body in parallel with each other; a plurality ofpairs of mutually slidable abutting surfaces distributed in saidconcrete wall member in parallel with each other, at least one of eachpair of abutting surfaces being formed by the elongated surface of saidbar member; and a plurality of subsections of the concrete wall memberbeing defined by severing said concrete wall body and said reinforcingmembers at said pairs of mutually slidable abutting surfaces, in such amanner that the concrete wall member has a rigidity which isdiscontinuous at said abutting surfaces and yet the concrete wall memberbeing a rigid integral wall as a whole unless a shearing load in excessof a certain yielding stress is applied thereto; the longitudinal lengthof said abutting surfaces and the distribution of said steel reinforcingmembers being so related that said abutting surfaces act to prevent eachsubsection fRom swelling when a stress greater than said yielding stressbut smaller than a breakdown stress thereof is applied thereto.
 2. Asteel reinforced concrete wall according to claim 1, wherein saidreinforcing concrete members in each subsection being so distributedthat each subsection has a shearing breakdown stress (Kg/cm2) which isgreater than a bending yielding stress (Kg/cm2) of the same subsection.3. A steel reinforced concrete wall according to claim 2, wherein eachof said subsection has a ductility factor not smaller than three, saidductility factor being a (strain at breakdown)/(strain at yield) ratio.4. A composite building structure having a skeleton with a breakdownstrain sigma 1(radians) and a plurality of steel reinforced concretewalls joined to said skeleton, each of said steel reinforced concretewalls, comprising a concrete wall body; steel reinforcing membersdistributed in the concrete wall body to reinforce the body; a pluralityof elongated strap-like bar members, each having at least one elongatedsurface whose width taken in the direction of the thickness of theconcrete wall body being substantially identical with the thickness ofthe concrete wall body, said plurality of the bar members being embeddedin said concrete wall body in parallel with each other; a plurality ofpairs of mutually slidable abutting surfaces distributed in saidconcrete wall member in parallel with each other, at least one of eachpair of abutting surfaces being formed by the elongated surface of saidbar member; and a plurality of subsections of the concrete wall memberbeing defined by severing said concrete wall body and said reinforcingmembers at said pairs of mutually slidable abutting surfaces, in such amanner that the concrete wall member has a rigidity which isdiscontinuous at said abutting surfaces and yet the concrete wall memberbeing a rigid integral wall as a whole unless a shearing load in excessof a certain yielding stress is applied thereto; the longitudinal lengthof said abutting surfaces and the distribution of said steel reinforcingmembers being so related that said abutting surfaces act to prevent eachsubsection from swelling when a stress greater than said yielding stressbut smaller than a breakdown stress thereof is applied thereto, saidreinforcing concrete members in each subsection being so distributedthat each subsection has a shearing breakdown stress (Kg/cm2), which isgreater than a bending yielding stress (Kg/cm2) of the same subsection,and a ductility factor not smaller than three, said ductility factorbeing a (strain sigma 2(radian) at breakdown)/(strain sigma 2(radian) atyield) ratio, whereby said composite building structure has a breakdownstrain sigma 3(radian) which is identical with the sum of said skeletonbreakdown strain sigma 1(radian) and said wall subsection breakdownstrain sigma 2(raidan) ( sigma 3 sigma 1+ sigma 2).
 5. A steelreinforced concrete wall according to claim 1, wherein each of said barmembers is made of a material selected from the group consisting ofasbestos slates, plaster boards, synthetic resin, iron, and non-ferrousmetals.
 6. A steel reinforced concrete wall according to claim 5,wherein each of said bar members consists of a single bar made of amaterial selected from said group.
 7. A steel reinforced concrete wallaccording to claim 5, wherein each of said bar members consists of twobars made of a material selected from said group.
 8. A steel reinforcedconcrete wall according to claim 1, wherein said concrete wall body isof rectangular shape including one side length of (l + 2l0), and thelength of each of said strap-like bar members is l, and the bar membersare disposed in said concrete wall member with a uniform spacings of Dbetween each other in parallel with said wall member side of length (l +l0) while leaving a spacing l0 from other sides of the wall member tofacing ends of the bar member, the dimensions D, l, and l0 satisfyingconditions of l0/D > or = 0.5 and l/D > or = 1.0.
 9. A composite wallstructure according to claim 4, wherein natural period T (second) of theskeleton is related to the height H (meter) of the skeleton as follows:T > or = 0.025H.
 10. A composite building structure according to claim4, wherein said skeleton is a steel skeleton.
 11. A steel reinforcedconcrete wall according to claim 1, wherein said subsections are precaststeel reinforced concrete wall sections, and said strap-like bar membersare disposed at joints between the adjacent precast wall sections.
 12. Acomposite wall structure according to claim 4, wherein said steelreinforced concrete wall members are disposed in at least two verticalrows in parallel with vertical columns of said skeleton.
 13. A steelreinforced concrete wall according to claim 1, wherein said strap-likebar member is coated with a friction-reducing film.
 14. A steelreinforced concrete wall according to claim 8, wherein each saidstrap-like bar members is divided in two parts which are spaced fromeach other in the longitudinal direction thereof.
 15. A steel reinforcedconcrete wall according to claim 1, wherein said strap-like bar membersextend from one edge of the wall body toward the opposite edge to saidone edge and terminate at an intermediate position before reaching theopposite edge.
 16. A steel reinforced concrete wall according to claim1, wherein said strap-like bar members extend from each of the twoopposing edges of the wall body by a length shorter than one half of thedistance between the two opposing edges.